Platelet Aggregation in Patients With Diabetic Retinopathy Evaluated With a Particle Counting Method Using Light Scattering

Abstract

Abstract: : Purpose: Increased platelet aggregation has been shown in patients with diabetes mellitus, but correlation between platelet aggregation and severity of diabetic retinopathy has not been reported. Spontaneous platelet aggregation (SPA) formed in the absence of chemical stimulants, which cannot be done using the conventional optical density method, can be quantified with a novel platelet aggregometer, using light scattering method. We quantified platelet aggregates in various stages of diabetic retinopathy with this light scattering method. Methods:SPA was measured in 21 patients with untreated non-diabetic retinopathy (NDR), 10 with simple diabetic retinopathy (SDR), 15 with pre-proliferative diabetic retinopathy (PPDR), 19 with proliferative diabetic retinopathy (PDR), and 32 healthy volunteers (Control), with a light-scattering platelet aggregometer (PA200, Kowa, Japan). Platelet aggregates were classified into three sizes according to light intensity: small (25-400), medium (400-1000), and large (1000-2048). Total light intensities of each aggregate size (small, medium, and large) were compared among the 5 groups (Fisher's PLSD). Results:NDR showed a significant increase in small-size aggregates as compared with Control and PDR (21.3x10⁶ v.s. 8.3x10⁶ : p=0.001; 21.3x10⁶ v.s. 12.0x10⁶ : p=0.039). SDR, PPDR and PDR showed a significant increase in small, medium and large-size aggregates, respectively, as compared with Control (19.5x10⁶ v.s. 8.3x10⁶ : p=0.029; 3.7x10⁵ v.s. 1.1x10⁵: p=0.009; 2.9x10⁵ v.s. 1.5x10⁵: p=0.046). Conclusions:Small-size platelet aggregates increased before evident diabetic retinopathy occurred. Aggregates' sizes showed a tendency to increase with severity of diabetic retinopathy, indicating that they might take part in the progression of diabetic retinopathy.

Keywords: diabetic retinopathy